I had just bought a 74 302 block from a machine shop and had them bore it .60 over. Was that a mistake or m I still ok to proceed with my build. Not building a race car just a Sunday driver.
Some folks have had overheating issues with a .060 over bored block, others report no issues, may depend on other factors, personally I wouldn't/didn't want .060 over on my 351w for fear of overheating issues.
A .060 overbore is not a reason to overheat, generally problem stems from a more powerful engine and a marginal cooling system..
the trouble with 60 over is youve shaved the chance of another rebuild out of it. you wouldve been happy with 40 over and a good cam carb and intake but its done so build it an have fun with it
If the block was of good integrity to begin with, 060 over should be okay. I've heard that the Mexican blocks are a bit more beefy and are better for such an over-bore. With that said, it has always been recommended to not exceed 040 over on a small-block Ford. I don't think you'll have cooling problems if your cooling system is up to snuff, but personally, I would have gone no more than 040.
Hopefully before they bored it the shop measured the cylinder walls thickness. There's a reason these are referred to as "thin wall castings". Not enough material and the cylinders flex. Me personally, I wouldn't use a stock block that's more than .030" over.
I had a bored over .60 302 for about 4 years in my Maverick and never had any problems with it and I had an edelbrock top end kit, but I also have a champion 3-core radiator too oh and it was ran hard too
Me either. Mild motors with stock strokes(power levels and rod ratio matter) will never even come close to taxing an over-bored "thin wall casting".
Assuming the block doesn't break a cylinder wall(which would no doubt be obvious), there should never be a overheating problem because of a .060 overbore... Why? Main reason is most all the heat generated is in the heads, maybe 10-15% of the heat is contributed by the cylinders... Any additional heat because of overbore would be minuscule, pistons are cooled more by oil splash than heat transferred into cylinder walls... A .060 over small block that overheats is either assembled with too tight clearances, or cooling system has issues...
It's not the .060 that creates a problem, it's core shift that'll get you into trouble. "Core shift" is what happens when the block casting was poured, the cylinder cores often end up "off centered" in the casting, so when the block is bored, you end up with walls that are thicker and thinner in the same cylinder. You can see this when looking at the bottom of the bores with the oil pan off. And the thing posted about the Mex blocks ? That's simply not true. Your 74 block has the same iron content as the Mex block, only difference here is the Mex had beefier main caps, as did the 289 HiPo block and the D8VE-A3A block. All the 302 blocks from 68-79 weighed in at 136 lbs.
Any block that is bored to 0.060 should be sonic checked core shift is a problem and is more of a problem if you get a thin wall on the stress side of the bore! There are lots of .060 over 302 engines living under normal conditions with out any problems! A high performance stroker wouldn't be a good idea with a 0.060 over bore! All small blocks do weigh the same up to 1979 but after 1974 the quality of the castings are not the same !
I've looked over the D8VE blocks, (two of em) and the quality is no different than the earlier blocks. Got a buddy that runs em in dirt cars, even he says they're good blocks, he wasn;t even aware of the D8 block before I handed over these two to him.
There may have been some good ones that were made after 1974 but the quality control was not as good! I bought a new Cobra II in 1977 ! When we went to rebuild the engine I tried to find a block that was date correct we tested 7 blocks non would pass the sonic test to be bored 0.03 over ! This may be ok for a 139 hp engine but for a 347 with more than 400 Hp you need a better block , We found one that passed it is a C 9 block From a bronco!
